Hi Moshin29
Have another option for you - and one you won't need to muck around with tubes.
Audio-gd NFB 15.32 (
http://www.audio-gd.com/Pro/Headphoneamp/NFB1532/NFB15.32EN.htm) currently USD235 + freight. I own the NFB-12 which is the older version of this amp. Whilst I haven't got (or heard) the DT990, I did own both the 250ohm and 600ohm DT880s - and the NFB-12 paired really nicely with them.
What I found with the Audio-gd is:
- Dual WM8741s mean sound is very full bodied (rather than lean and thin)
- A class amp section is very powerful
- Has inputs for USB, optical and coax
- Has outputs for headphone, and a DAC out (analog out) that can be either fixed or variable. Variable uses the volume pot on the Audio-gd.
At home I use the headphone out for my headphones, then the line-out (RCA's) through a splitter to either:
- LD MKIV full OTL tube amp (on the fixed line-out switch) - mainly for when I had the DT880 600ohm, for my HD600s, and eventually for the HD800s if/when I get them.
- My passive bookshelf speakers (Celestian F10s) (on the variable line-out switch)
It has no problems with the speakers - and is perfect with brighter cans (like the Beyers), but without making things too warm (ie - fantastic also with AKG, HD600 etc).
If you're looking at a DAC/amp combo that is budget friendly, able to drive most cans out there, and sounds great - I'd give the NFB 15.32 some consideration.